In recent years, the following lining materials have been used for pipelines similar to that described in the preceding Technical FIELD:
(1) A lining material having a tubular textile jacket provided on the outer surface thereof, in which the surface facing the inner surface of a pipeline is bonded to its inner surface while being turned inside out, and also with a film of a rubber or a synthetic resin (Japanese Laid-open Patent Appln. No. Sho. 56-8229 or Japanese Laid-open Utility Model Appln. No. Sho. 56-3619). (2) A lining material having the above-mentioned structure but having two layers of the tubular textile jacket (Japanese Laid-open Patent Appln. No. Sho. 59-225921). (3) A lining material having the above-mentioned structure wherein its tubular textile jacket is composed of a combination of a tubular textile jacket and a tubular woven or unwoven fabric (Japanese Laid-open Patent Appln. No. Sho. 59-225920).
The lining materials used previously are air-impervious that allows the lining material to be evaginated by fluid pressure. The lining material is strong enough to withstand the fluid pressure during evagination. Once evaginated a binder is applied in an amount sufficient to bond the lining material onto the inner surface of the pipe line. However, such lining materials cannot be said to fully satisfy the performance conditions required in this art.
One of the purposes of providing pipelines with a lining material is to make the pipelines earthquake-resistant. Namely, even if a pipe line is destroyed by earthquake, the lining material should not be destroyed and maintain by itself the a passageway for transporting the internal fluid such as gas or water while preventing any leakage of the fluid. Necessary for this purpose is that the lining material should have a high tenacity and strength and should be impregnated with a large amount of the binder so that the binder may be solidified with the lining material to form a pipeline within the pipe line which is not collapsed by external pressure but maintains its shape against external pressure. Accordingly, the lining material should desirably have a fibrous layer that can be impregnated with a large amount of a binder and an air-impervious layer of a rubber or a synthetic resin for bonding to the fibrous layer.
Conventional lining materials, as disclosed in Japanese Laid-open Utility Model Appln. Nos. Sho. 56-8229 and 56-3619 wherein the fibrous layer is only comprised of the tubular textile jacket, cannot be impregnated with a sufficient amount of the binder in the lining treatment. Thus, it is impossible to obtain a sufficiently thick layer of the solidified binder to form a pipe capable of withstanding external pressure. The lining material as disclosed in Japanese Laid-open Patent Appln. No. Sho. 59-225921, wherein two layers of the tubular textile jacket are impregnated with a larger amount of the binder, is incapable of maintaining its shape in the against external pressure.
The lining material as disclosed in Japanese Laid-open Patent Appln. No. Sho. 59-225920, wherein the tubular textile jacket is provided on the inner surface thereof with a thick layer of an unwoven fabric, can be impreganted with a large amount of the binder and forms a thick cured binder layer when bonded to the pipeline. On the other hand, however, the manufacture of this lining material is very difficult requiring a long unwoven fabric made in a tubular form by sewing should be inserted into a long textile jacket woven in a tubular form. In addition, the manufacture of a long tubular unwoven fabric is troublesome and needs a plurality of difficult steps since a tubular unwoven fabric cannot be manufactured directly, but can be manufactured only by sewing both edges of the unwoven fabric in the form of a sheet. In the case of a fabric combined with an unwoven fabric, the fabric is overlaid with the unwoven fabric and needle-punching is applied towards the surface of the unwoven fabric. Where a tubular textile jacket is provided on the inner surface thereof with a tubular unwoven fabric, it is impossible to apply needle-punching outwardly from the interior space of the tubular unwoven fabric. If needle-punching is applied inwardly from the outer surface of the tubular textile jacket, the tubular unwoven fabric will not bind to the tubular textile jacket and will slip during the process of manufacture or evagination of the lining material making it difficult to obtain a satisfactory quality of the lining material.